This invention relates to recovering carbon dioxide from an ethylene oxide production process. In particular this invention relates to recovering carbon dioxide from an ethylene oxide production process and using the recovered carbon dioxide to produce methanol.
Ethylene oxide is a major chemical raw material. Presently, about 9.6 million tons of ethylene oxide are produced world wide each year. The major use of ethylene oxide is for the manufacture of derivatives such as ethylene glycol, surfactants, and ethanolamines.
In the production of ethylene oxide 20-25% of the ethylene feed is oxidized into carbon dioxide and water instead of ethylene oxide. The loss of large quantities of ethylene and the environmental concerns in purging carbon dioxide into the environment has lead to attempts at minimizing the amount of carbon dioxide produced during the ethylene oxide production process.
Most of these efforts have concentrated on the selection of inhibitors and catalysts to increase ethylene oxide selectivity. For example, U.S. Pat. No. 5,102,848 to Soo et al. discloses the addition of fluoride anion to a catalyst reduces ethylene oxide combustion to carbon dioxide. U.S. Pat. No. 3,585,217 to Titzenthaler discloses that alkali metal chlorides can be used to counteract the formation of carbon dioxide during ethylene oxide production.
Instead of limiting the production of carbon dioxide during the ethylene oxide production process, the present invention provides for recovering the carbon dioxide. The recovered carbon dioxide is then used to produce methanol.
This invention provides a method of using carbon dioxide produced in an ethylene oxide reaction unit to produce methanol. Carbon dioxide produced during ethylene oxide production is used to produce syngas which is used to produce methanol.
In one embodiment, the invention provides a method of making methanol. The method comprises obtaining a carbon dioxide stream from an ethylene oxide production process, producing a syngas stream incorporating the carbon dioxide stream, and producing methanol from the syngas stream.
Preferably, the syngas stream produced has an SN from about 1.4 to about 2.4. Preferably, the syngas is produced using a steam reformer or a partial oxidation reformer. Preferably, the methanol produced is used as a feed to an olefin synthesis reactor. Preferably, the olefin synthesis reactor contains a molecular sieve catalyst selected from SAPO-5, SAPO-8, SAPO-11, SAPO-16, SAPO-17, SAPO-18, SAPO-20, SAPO-31, SAPO-34, SAPO-35, SAPO-36, SAPO-37, SAPO-40, SAPO-41, SAPO-42, SAPO-44, SAPO-47, SAPO-56, the metallic containing forms thereof, or mixtures thereof. Preferably, the ethylene oxide production process comprises the catalytic oxidation of ethylene in the presence of a supported silver-based catalyst.
In another embodiment, the invention provides another method of making methanol. The method comprises introducing an ethylene stream into an ethylene oxide reaction unit and forming an ethylene oxide product within the ethylene oxide reaction unit. An ethylene oxide product stream and a carbon dioxide-containing vent stream are removed from ethylene oxide reaction unit. The carbon dioxide vent stream is used to produce a syngas stream. The syngas stream is used to produce methanol.
This invention will be better understood in combination with the following detailed description, and appended drawing and claims.